SITE INFORMATION AND CORRESPONDENCE

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• MEMORANDUM * CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION 3443 Roufier Road, Suite A Phone: (916) 361-5600 Sacramento, CA 95827-3098 ATSS Phone: 8-495-5600 TO: GREG VAUGHN FROM: JEAN McCUE Senior Engineer Water Resource Control Engineer MAR 1 1 1 DATE: 28 February 1991 SIGNATURE: SUBJECT: CLOSURE PLAN FOR R£-MANUFACTURING SURFACE IMPOUNDMENT, STOCKTON, SAN JOAQUIN COUNTY On 14 December 1990, Kleinfelder submitted two reports on behalf of Mr. Stanley Moore of Re-Manufacturing: "Soil and Ground Water Assessment" and "Closure Plan for Re-Manufacturing Surface Impoundment" . The reports were submitted to satisfy two requirements of Administrative Civil Liability Order No. 90-236. Following is a description of and comments on the Closure Plan: The stated objective in the plan is to document the means by which the surface impoundment (SI) can be closed so that migration of residual contaminants will not pose a threat to the environment. The closure plan must also comply with California Code of Regulations, Title 23, Division 3, Chapter 15 (Chapter 15) requirements. Kleinfelder states in the plan that it appears the SI has not affected soil more than a few feet below the SI floor. Four borings sampled through the SI floor on 24 August 1989 support this statement, in terms of lead. However, it must be kept in mind that lead is only an indicator parameter. Odd occurrences of other contaminants were found at greater depths (see attached table) . Re-Manufacturing has not determined how far the contamination extends in the sidewalls. According to the report, Re-Manufacturing excavated a portion of the contaminated soil from the SI in 1990. The current dimensions of the SI are roughly 40 feet by 100 feet and 10 to 12 feet deep. Re- Manufacturing estimates that 40 to 60 tons of contaminated soil was transported to a hazardous waste landfill and 120 cubic yards of contaminated soil is currently stockpiled on site. On 30 November 1990, soil samples were collected from the sidewalls and floor of the SI to assess the concentrations of total and soluble lead remaining after excavation. Sample results show that hazardous levels of total lead remain in the SI. The highest concentrations were found in samples collected from the north and east sidewalls of the SI, which contained total lead in concentrations of 44,000 mg/kg and 62,700 mg/kg respectively. This is well above the Total Threshold Limit Concentration (TTLC) for lead, which is 1,000 mg/kg. Selected samples were also analyzed for soluble lead, using the de-ionized water (DI) Waste Extraction Test (WET) . The OI-WET results were non-detectable (below the detection limit of 0.50 mg/1 ) in all samples analyzed. No citrate WETS were performed on the samples from the SI . Samples were also collected from the stockpiled excavated soils. Those samples were analyzed for total and soluble lead, using both the citrate and DI-WET. The concentrations of soluble lead in the stockpile samples, using the citrate WET, were as high as 215 mg/l (from the same sample containing a total lead concentration of 7,040 mg/kg) . The Soluble Threshold Limit Concentration (STLC) for lead is 5 mg/l .